Robotic radiosurgery systems, such as CyberKnife™, use a high-precision robotic manipulator, with an image-guided system delivering beams of radiation to the target from multiple predefined beam directions. Since the total clinical precision of robotic radiosurgery treatment ultimately depends on the accuracy and reproducibility of each beam direction, the quality assurance (QA) of beam geometry is of paramount importance. The current method (old) of verifying the predefined beam geometry involves directing the internal laser onto the crystal of an iso-post and adjusting beam position based on the signal generated from the crystal, until the maximum signal is reached. Since the crystal is affixed at the system's iso-center, the old procedure is designed to ascertain the alignment of the beam central axis with the system's iso-center. However, there are several drawbacks to this method: first, the precise laser alignment must be achieved, which is a difficult task, second, the old method does not yield beam angular information, third, it does not yield information about the distance between the radiation source and the system's iso-center (SAD), and fourth, the beam adjustment is a random search process which makes the procedure time-consuming.
This invention was conceived to access full beam geometric parameters by radiographic visualization of the beam central axis. The procedure designed for using this device reveals the inaccuracy of the imaging system and the error in robotic precision. Once the imaging system is independently calibrated, the new apparatus and method provides information to adjust the beam geometry to the optimum specification.